Muffler with dual expansion chambers



Get. 5, 1965 E. c. LENTZ MUFFLER WITH DUAL EXPANSION CHAMBERS Filed Oct. 51. 1961 .W@ R. 2 r V e a m n United States Patent Office ufacturing Company, Racine, Wis., a corporation of Delaware Filed Oct. 31, 1961, Ser. No. 149,072 6 Claims. (Cl. 181-57) This invention relates to mufflers and in particular to a small economical lawn mower muffler having improved muifling characteristics.

Heretofore small lawn mower mufl lers as well as larger mufiiers have not been made so that they may be readily disassembled by the customer for cleaning. This has been largely due to the thought that proper sealing of the mufller parts could not readily and economically be obtained by means other than providing flanges on the parts and then clamping them together such as by turning one flange over the other and mechanically deforming it tightly against the other.

The main objects of the present invention are: to provide a lawn mower muffler which can be readily assembled and disassembled and which is so constructed that gastight seals between the various parts of the mufller can readily be obtained; to provide a mufller having shell sections of such construction that they may be formed in the same die; to provide a muffler center tube which is formed with threaded ends to provide means for attaching the muffler to an engine while simultaneously securing the separate parts of the muffler in assembled relation ship; and to provide a niuifler of only five parts which form a pair of expansion chambers, the required gas flow apertures, and an inlet and outlet.

Further objects, advantages, and novel features of the invention will become apparent from the following description taken in conjunction with the drawing wherein:

FIGURE 1 is a longitudinal sectional view of the mufiler; and

FIG. 2 is a cross-sectional view of the mufller taken along the line 22 of FIGURE 1.

In the drawing:

The muflier 10 comprises cup-shaped shell sections 12 and 14 both of which may be formed in the same drawing die. One of these sections, however, such as 14 as shown, is thereafter formed with a rim portion 16 to provide a shoulder 18 and a beveled sealing surface 20. Sections 12 and 14 are provided respectively with apertures 22 and 24 for receiving a center tube 26 in relatively tight frictional engagement so as to prevent excessive gas leakage thereby.

A divider plate 28 is formed with a peripheral flange portion 30 formed with a curved inner surface portion 32 and a curved outer surface portion 33. A circular aperture 34 in plate 28, which is otherwise imperforate, forms an annular slot 36 in cooperation with center tube 26 when the muffler is assembled with the bottom portion 37 of the divider plate abutting shoulder 18, and the surface portion 33 thereof frictionally and sealingly engaging the beveled rim as at 20. The outer edge 38 of section 12 engages the surface portion 32 of plate 28 and frictionally seals thereagainst when the mufller is assembled.

The center tube 26 is pinched as at 40 to provide an inlet portion 42 and an outlet portion 44 respectively formed with apertures 46 and 48. The ends of the tube are formed with threads 50 and 52 preferably by rolling.

In assembling the muffler onto an engine 53, the center tube is threaded into a threaded portion 54 of the engine exhaust passage 56, and the muffler sections 12, 14, and 28 are then assembled over the tube 26. A nut 58 is then threaded onto the tube threads 52 to tightly engage the 3,208,860 Patented Oct. 5, 1965 bottom 59 of section 14 to press the mufller portions together in sealing relationship. Since the user rather than the manufacturer assemblies the muflier, manufacturing and shipping costs are reduced. The user can also disassemble the unit to clean it out.

The apertures 46 and 48 are respectively located adjacent the inner portion 60 of the first expansion chamber 64 and the outer portion 62 of the second expansion chamber 66. This location of the single apertures 46 and 48 facilities manufacture and provides more abrupt expansion and travel of the gas in each of these chambers prior to its emission therefrom. The annular slot 36 which is conveniently formed by providing an aperture in the divider plate and then inserting the center tube therethrough, improves the mufiler acoustics. This slot functions to restrict the flow of gas into the second expansion chamber 66 and thereby absorbs additional energy from the gas after it has been expanded into chamber 64 and somewhat cooled therein. The subsequent abrupt expansion and cooling of the gas in chamber 66 further reduces the energy of the exhaust pulsations.

While it will be apparent that the embodiment of the invention herein disclosed is well calculated to fulfill the objects of the invention, it will be appreciated that the invention is susceptible to modification, variation and a change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. A mufiier comprising two cup-shaped shell sections having ends in nested arrangement, a divider plate extending across the ends of said sections and having peripheral portions intermediate said ends and in nested arrangement therewith, said plate and sections forming first and second expansion chambers, said plate having an aperture therein, each of said sections having a bottom with an aperture therein, all of said apertures being substantially aligned, a center tube extending through said apertures and having a closed portion lying within said first chamber and forming an inlet portion and an outlet portion, each of said center tube portions having an aper ture therein, the aperture in said plate being larger than said center tube to form therewith a gas flow port connecting said chambers.

2. A mufiier comprising two cup-shaped shell sections having ends in nested arrangement, a divider plate extending across the ends of said sections and having peripheral portions intermediate said ends and in nested arrangement therewith, said plate and sections forming first and second expansion chambers, said plate having an aperture therein, each of said sections having a bottom with an aperture therein, all of said apertures being substantially aligned, a center tube extending through said apertures and having a closed portion lying Within said first chamber and forming an inlet portion and an outlet portion, each of said center tube portions having an aperture therein, the aperture in said plate being larger than said center tube to form therewith a gas flow port connecting said chambers, said center tube having threaded ends outside said sections to provide means for clamping the sections together against the plate.

3. A mufller comprising two cup-shaped shell sections having ends in nested arrangement, a divider plate extending across the ends of said sections and having peripheral portions intermediate said ends and in nested arrangement therewith, said plate and sections forming first and second expansion chambers, said plate having an aperture therein, each of said sections having a bottom with an aperture therein, all of said apertures being substantially aligned, a center tube extending through said apertures and having a closed portion lying within said first chamber and forming an inlet portion and an outlet portion, each of said center tube portions having an aperture therein, the aperture in said plate being larger than said center the to form therewith a gas flow part connecting said chambers, one of the tube ends being threaded for receiving a nut and the other end being threaded and adapted to be threadably received in a threaded socket in an engine.

4. A mutfier comprising two cup-shaped shell sections having ends in nested arrangement, a divider plate extending across the ends of said sections and having peripheral portions intermediate said ends and in nested arrangement therewith, said plate and sections forming first and second expansion chambers, said plate having an aperture therein, each of said sections having a bottom with an aperture therein, all of said apertures being substantially aligned, a center tube extending through said apertures and having a closed portion lying within said first chamber and forming an inlet portion and an outlet portion, said inlet portion having an aperture close to the bottom of said first chamber, said outlet portion having an aperture close to the bottom of said second chamber, the aperture in said plate being larger than said center tube to form therewith a gas flow port connecting said chambers. V

5. A muffler comprising two cup-shaped shell sections having ends in nested arrangement, a divider plate extending across the ends of said sections and having peripheral portions intermediate said ends and in nested arrangement therewith, said plate and sections forming first and second expansion chambers, one of said sections having an outwardly flared rim frictionally receiving said peripheral portions of said plate to form a rnetal-to-rnetal seal therebetween, said plate having an aperture therein, each of said sections having a bottom with an aperture therein, all of said apertures being substantially aligned,

a center tube extending through said apertures and having a closed portion lying within said first chamber and forming an inlet portion and an outlet portion, each of said center tube portions having an aperture therein, the aperture in said plate being larger than said center tube to form therewith a gas fiow port connecting said chambers.

6. A muffler comprising two cup-shaped shell sections having ends in nested arrangement, a divider plate extending across the ends of said sections and having peripheral portions intermediate said ends and in nested arrangement therewith, said plate and sections forming first and second expansion chambers, one of said sections having an outwardly flared rim frictionally receiving said peripheral portions of said plate to form a metal-to-metal seal therebetween, said peripheral portions being formed with a flange and frictionally receiving the outer end of the other section in a frictional manner to form a metalto-rnetal seal, said plate having an aperture, each of said sections having a bottom with an aperture therein, all of said apertures being substantially aligned, a center tube extending through said apertures and having a closed portion lying within said first chamber and forming an inlet portion and an outlet portion, each of said center tube portions having aperture means, the aperture in said plate being larger than said center tube to form therewith a gas flow port connecting said chambers.

References Cited by the Examiner UNITED STATES PATENTS 938,860 11/02 Hicks 181-57 749,883 1/04 Russell 18153 1,173,583 2/16 Johnston et al l8145 1,761,471 6/30 Forstel 18147 1,900,027 3/33 Radecky 181-49 2,218,063 10/40 Munzer. 2,962,110 11/60 Depman 18156 X FOREIGN PATENTS 733,047 3/43 Germany. 280,719 1 1/ 27 Great Britain.

LEO SMILOW, Primary Examiner.

CARL w. ROBINSON, Examiner. 

1. A MUFFLER COMPRISING TWO CUP-SHAPED SHELL SECTIONS HAVING ENDS IN NESTED ARRANGEMENT, A DIVIDER PLATE EXTENDING ACROSS THE ENDS OF SAID SECTIONS AND HAVING PERIPHERAL PORTIONS INTERMEDIATE SAID ENDS AND IN NESTED ARRANGEMENT THEREWITH, SAID PLATE AND SECTIONS FORMING FIRST AND SECOND EXPANSION CHAMBERS, SAID PLATE HAVING AN APERTURE THEREIN, EACH OF SAID SECTINS HAVING A BOTTOM WITH AN APERTURE THEREIN, ALL OF SAID APERTURES BEING SUBSTANTIALLY ALIGNED, A CENTER TUBE EXTENDING THROUGH SAID APERTURES AND HAVING A CLOSED PORTION LYING WITHIN SAID 